The present invention relates to a method for producing BGA (ball grid array) type semiconductor devices, more particularly such BGA type semiconductor devices each of which is substantially made of semiconductor die mounting substrate which mounts a lead pattern on one surface thereof while making the other surface thereof adhered to a metal substrate which has a region on which a semiconductor die is mounted and the semiconductor devices produced by such a method.
Conventionally, the semiconductor devices such as IC (integrated circuit) and LSI (large scaled integrated circuit) are mounted in such a manner that a plurality of outer leads which are formed in a desired shape such as a J-shape or a gull-wing shape along an outer periphery of the semiconductor device are protruded outwardly and such outer leads are connected with corresponding mounting pads (or lands) of a wiring pattern formed on a mounting board of a printed wiring board (PWB) by soldering. This method, however, necessitates a relatively wide mounting region so that the method cannot meet a demand for compacting of the semiconductor devices.
For overcoming this drawback, recently, the semiconductor devices called BGA which use a plurality of solder balls as the outer connecting terminals of semiconductor devices thus realizing miniaturing of semiconductor dies, down-sizing of the semiconductor devices and lowering of the production cost of the semiconductor devices have been proposed. Such devices are, for example, disclosed in U.S. Pat. specification No. 5,045,921 (Lin et al.), U.S. Pat. No. 5,216,278 (Lin et al), U.S. Pat. No. 5,397,921 (Karnezos), U.S. Pat. No. 5,420,460 (Massingill), Japanese laid-open patent publication HEI 3-99456 and Japanese laid-open patent publication HEI 4-277636. In mounting such semiconductor devices on the mounting board, soluble solder balls of each semiconductor device are first aligned with corresponding mounting pads or lands of the mounting board and subsequently are mounted on the mounting pads and the soluble solder balls are reflown by heating thus enabling a simultaneous mounting of all solder balls to the mounting pads of the mounting board facilitating the mounting of semiconductor devices on the mounting board.
The above-mentioned BGA type semiconductor devices have been produced, for example, by a following method.
Namely, using an etching method, a lead pattern made of first conductive leads and a die mounting region is formed on one surface of a TAB (Tape Automated Bonding) substrate or a glass fabrics reinforced epoxy resin substrate while a lead pattern made of second conductive leads is mounted on the other surface of the substrate thus producing a semiconductor die mounting substrate or a semiconductor chip carrier. On the surface of the semiconductor die mounting substrate which is provided with the lead pattern made of first conductive leads, a face-up type semiconductor die is mounted, wherein a plurality of electrode pads mounted on the surface of the semiconductor die are connected with a plurality of corresponding conductive leads by means of bonding wires made of, for example, gold wires to provide an electric conductive circuit.
Subsequently, an overmolding or a transfer resin molding is carried out so as to hermetically and integrally seal the semiconductor die, the bonding wires and the lead pattern made of the first leads thus producing a resin sealed body.
On the other surface of the semiconductor die mounting board which provides a lead pattern forming face and is provided with the second conductive leads which in turn are connected with the first conductive leads by way of through holes, a solder resist layer is formed while leaving terminal portions of the conductive leads being arrayed in a grid like circuit pattern exposed to an atmosphere by way of spaces. Then, the soluble solder balls are mounted in the spaces and such solder balls are heated and reflown to establish an electrical connection with the terminal portions of the conductive leads thus producing a semiconductor devices having ball-shaped outer terminals protruding outwarly from the lead pattern forming surface.
In the above-mentioned conventional method for producing the semiconductor devices, however, since the TAB board substrate or the glass fabrics reinforced epoxy resin substrate is used as the semiconductor chip carrier, the method is less than optimal in terms of dissipation of high temperature.
Furthermore, since the method uses the overmolding which provides a sealing mold only on one surface of the semiconductor die mounting substrate, the semiconductor device having a specific construction is bent or warped in an arc shape due to a thermal shrinkage of the resin thus the method cannot assure the uniformity in coplanality of the solder balls.
Still furthermore, as the resin and the circuit substrate are subjected to heating and cooling, due to the difference of the heat expansion rate between these two materials, the peeling off and cracks occur in the resin sealed body, thus giving rise to lowering of the production of the semiconductor devices thus hampering the productivity thereof.
Accordingly, it is an object of the present invention to provide a method for producing semiconductor devices, especially BGA type semiconductor devices which can overcome the above-mentioned drawbacks of the conventional method, wherein the method is preferably used in the manufacturing of semiconductor mounting substrates and can improve the trasferring and positioning efficiency at the time of mounting semiconductor dies on the semiconductor die mounting substrates thus enhancing the mounting of semiconductor dies and eventually the productivity of the semiconductor devices.
It is another object of the present invention to provide semiconductor devices which can be produced at a low cost with a high reliablity in mounting.